1. Field of the Invention
This invention general relates to multicarrier communication systems. In particular, this invention relates to systems and methods that allow a transmitter to enter and exit a Q-Mode.
2. Description of Related Art
Q-mode is being examined by ADSL standards bodies in the ITU-T in the development of the G.dmt.bis and G.lite.bis ADSL standards, both of which are incorporated herein by reference in their entirety. Q-mode is a low power transmission mode intended to save power by transmitting signals with lower PAR (Peak to Average power Ratio) with respect to normal steady state, i.e., full power, signals. The Q-mode signal with low PAR will often have the same average power as the normal steady state signals but since the peak power is reduced, power consumption can be reduced in the analog transmission circuitry. This is very important especially for saving power in telephone company central offices and remote cabinets where ADSL modems are often installed.
Current Q-mode proposals utilize a Q-mode “filler” symbol with low PAR properties in order to save power at the transmitter. Discussion of this type of approach can be found in various ITU Documents, such as, BA-044, BA-045, HC-029R1, CF-033 and CF-040, all of which are incorporated herein by reference in their entirety. Other ITU proposals state that the filler symbol should be defined by the transmitter and communicated to the receiver during initialization, see BI-080 and D.87, both of which are also incorporated herein by reference in their entirety.